Carbon monoxide rich synthesis gases with hydrogen to carbon monoxide ratios below or around 1.5, typically below 1, are produced by gasification of coal, petroleum coke, oils and biomass. For the purpose of conversion of the carbon monoxide rich synthesis gas into chemicals and/or fuels a pre-adjustment of the synthesis gas with respect to hydrogen to carbon monoxide ratio and carbon dioxide content is typically performed in order to meet the required stoichiometry for the desired product. Pre-adjustment may involve one or more of the steps of water gas shift, adjustments by membranes or washes and purging. As very often the desired hydrogen to carbon monoxide ratio of the synthesis gas utilised is well above 1 a typical means of synthesis gas adjustment is the water gas shift conversion followed by removal of excess CO2 e.g. by absorption in a liquid medium by well known processes such as the Rectisol®, Selexol® or methyl diethanol amine (MDEA) washes. A disadvantage of these processes is that large amounts of carbon dioxide are vented.
The synthetic gasoline process as an example is known to take place in two steps: the conversion of synthesis gas to oxygenates and the conversion of oxygenates to gasoline product. These process steps may either be integrated, producing an oxygenate intermediate, e.g., methanol or methanol dimethyl ether mixtures, which along with unconverted synthesis gas is passed in its entirety to the subsequent step for conversion into gasoline (J. Topp-Jørgensen, Stud. Surf. Sci. Catal. 36 (1988) 293) or the process may be conducted in two separate steps with intermediate separation of oxygenates, e.g. methanol or raw methanol (S. Yurchak, Stud. Surf. Sci. Catal. 36 (1988) 251).
Preferred oxygenates include methanol, dimethyl ether and higher alcohols and ethers thereof, but also oxygenates like ketones, aldehydes and other easily convertible oxygenates may be applied.
In either case conversion of synthesis gas to oxygenates involves heat development in that both the conversion of synthesis gas to oxygenate and the further conversion of oxygenate to gasoline product are exothermic processes.
An integrated Fischer-Tropsch (FT) process and power production from carbonaceous materials by passing the material through a syngas generation unit, an air separation unit, a Fischer-Tropsch unit, a CO2 removal unit and a combined cycle electricity generation unit is disclosed in U.S. Pat. No. 6,976,362. Produced carbon dioxide is collected for sale or sequestration up stream of the electricity generation unit.
The production of gasoline by the integrated process scheme is also discussed in U.S. Pat. No. 4,481,305. Hydrocarbons and especially as gasoline are prepared by catalytic conversion in two subsequent reactors of a synthesis gas containing hydrogen and carbon oxides and having a mole ratio CO/H2 above 1 and when the conversion commences a mole ratio CO/CO2 of 5 to 20. Synthesis gas is converted with high efficiency in a first step into an oxygenate intermediate comprising predominantly dimethyl ether (DME) said mixture being converted in a second step into gasoline by the net reaction scheme3H2+3CO->CH3OCH3+CO2+Heat  (1)CH3OCH3->1/n(CH2)n+H2O+Heat  (2)
(CH2)n represents the wide range of hydrocarbons produced in the gasoline synthesis step. After separation of the hydrocarbon product, unconverted synthesis gas comprising hydrogen and carbon oxides is recycled to the oxygenate synthesis step after CO2 is at least partly removed in a CO2 wash.